JPH07194191A - Motor driver - Google Patents

Abstract

PURPOSE:To minimize the power consumption of a motor driver by dropping the voltage inputted for controlling the voltage applied across the motor driver to a prescribed value based on the count value of a counter circuit. CONSTITUTION:The outputs IN1-IN4 of a microcomputer 6 sent to driver circuits 1 and 2 are inputted to a detector 9. When one of the outputs IN1-IN4 is inputted, the detector 9 sends a resetting pulse having a certain width to a timer circuit 10 by driving a monostable multivibrator. The circuit 10 counts clock pulses and is reset whenever this resetting signal is inputted. Accordingly, the count value of the circuit 10 varies depending upon the periods of the outputs IN1-IN4. Switching elements 15-18 are turned on or off in accordance with the count value of the circuit 10 and the control voltages applied to the driver circuits 1 and 2 are decided by the turned-on/off states of the elements 15-18. Therefore, the voltage corresponding to the rotating speed of a motor 5 is applied to the motor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive device for driving a pulse motor.

[0002]

2. Description of the Related Art A pulse motor, which is also called a stepping motor, can accurately control the rotation angle and the rotation speed as compared with a general DC motor.
It has been widely used as a drive source for equipment A, and in recent years, it has also been widely used as a drive source for optical systems such as video cameras.

FIGS. 5 and 6 show an example of a focus motor driving device for adjusting the optical system of a video camera at present.

In FIG. 5, 1 and 2 are driver circuits,
3 and 4 are coils in the pulse motor, 5 is a magnet in the pulse motor, 6 is a microcomputer (hereinafter referred to as a microcomputer), and 7 and 8 are resistors.

FIG. 6 shows the internal structure of the driver circuits 1 and 2 shown in FIG. In FIG. 6, 101 and 102 are PNPs.
Transistors, 103 and 104 are NPN transistors,
105, 106, 107, and 108 are diodes, and 109
110 is an operational amplifier (hereinafter referred to as an operational amplifier), 1
11, 112, 113, 114, 115, and 116 are resistors, 117 and 118 are NOT gates, and 119 and 120 are AND gates.

In FIG. 6, the input IN1 is at "H" level,
When IN2 is at "L" level, a transistor (hereinafter abbreviated as Tr), 104 is in an ON state, Tr103 is in an OFF state, the operational amplifier 109 is enabled, and the base current of Tr101 is controlled, and the operational amplifier 110 is disabled. Then, the Tr 102 is turned off.

Therefore, a positive voltage is applied to OUT1 and a negative voltage is applied to OUT2, and a current flows through the load connected between them. At this time, the voltage V ₁₂ between OUT1 and OUT2 is detected by the resistors 111 and 112 and fed back to the operational amplifier 109,

[0008]

[Equation 1]

Is controlled so that However, R ₁₁₁ , R
₁₁₂ is the resistance value of the resistors 111 and 112, respectively.

On the other hand, when the input IN1 is "L" and IN2 is "H", contrary to the above, Tr101 and 104 are in OFF state, Tr102 and 103 are in driving state and ON state, respectively, and outputs OUT1 and OUT2 are output. Outputs the same voltage with the opposite polarity to the above. Here, the resistors 113 and 114
Has a resistance value equal to that of the resistors 111 and 112, respectively.

When both inputs IN1 and IN2 are "L", all the transistors of Tr101, 102, 103 and 104 are turned off, and outputs OUT1 and OUT2.
Becomes a high impedance state.

When both inputs IN1 and IN2 are "H", both Tr103 and 104 are in the ON state and OUT
1 and OUT2 are short-circuited.

FIG. 7 shows the relationship between these inputs and outputs. These input / output relationships are the same for IN3, IN4, OUT3, OUT4, and V _{C2 of the} drive circuit 2 shown in FIG.

In order to drive the pulse motor, the two driver circuits described above are used to form the configuration shown in FIG. In FIG. 5, outputs A, A-, B, B- of the microcomputer are inputs IN1, IN2, IN3, IN4 of the driver circuits 1 and 2, respectively.
To the drive signal.

FIG. 8 shows drive signals and drive waveforms for general two-phase excitation. In FIG. 8, the area I is I
N1 and IN2 are at "H" level and "L" level, respectively, current flows from OUT1 to OUT2 in the coil 3, IN3 and IN4 are respectively "H" and "L", and OUT3 to OUT4 is in the coil 4. Current is flowing through.

In this case, the voltage applied to each coil is the input V
Determined by _C1 and V _C2 but, V _C1, V _C2 in this case is divided by a predetermined value by the power supply voltage V _CC resistance 7,8. In this state, IN1 and IN2 become "H" and "L", respectively, so that the current flowing in the coil 3 is reversed, the current in the coil 4 remains unchanged, and the magnet 5 of the pulse motor rotates one step.

Further, in the area C, IN3 and IN4 are changed to "L" and "H", respectively, the current flowing through the coil 4 is reversed, and the magnet 5 is rotated by another step.

The pulse motor is driven by repeating the above process. The microcomputer 6 generates changes and timings of the signal inputs IN1, IN2, IN3, IN4 provided to the driver circuits 1 and 2. Each coil 3
The voltage applied to 4 becomes a rectangular wave as shown in FIG.

On the other hand, the waveform that drives the pulse motor is considered to be the sine wave, which is the most efficient and smooth rotation, and the noise generated during the rotation is small. Therefore, the second conventional example shown below is considered. ing. This second conventional example will be described with reference to FIGS. 9 and 10.

FIG. 9 shows the configuration of the second conventional example.
The elements 1 to 6 are the same as those of the first conventional example shown in FIG. 5, and the outputs of DA1 and DA2 shown in the microcomputer 6 are the outputs of the DA converters incorporated in the microcomputer 6, respectively.

In FIG. 9, the microcomputer 6 is the IN of FIG.
1 · IN2 · IN3 · IN4 drive signal and V _C1 ·
The drive waveform signal shown at V _C2 is generated. V _C1 and V _C2 are continuous waveforms of the positive part of the sine wave, and the outputs of the driver circuits 1 and 2 are OUT1, OUT2, and OUT of FIG.
3, a sinusoidal drive waveform as shown by OUT4 is obtained.

The above-described conventional example is used as a driving device of an autofocus system for adjusting an optical system of a video camera, for example. However, when the focus state is recognized to be in focus in the autofocus system, The motor may be temporarily stopped at the rotational position until it is recognized that something has changed in the subject. The voltage applied to the motor at this time is kept constant at the voltage at that time.

FIG. 11 shows the relationship between the rotation speed of the pulse motor and its torque. As shown in FIG. 11, if the applied voltage is constant, the higher the rotation speed, the smaller the rotation torque. In the autofocus system, the applied voltage is adjusted so that sufficient rotation torque can be obtained at the maximum rotation speed required for the system. Has been set. Therefore, when stopping the motor at a certain rotational position as described above, if the applied voltage at the stopped state, that is, the rotational speed of 0 is the same as that at the time of maximum speed rotation, the applied voltage exceeds the necessary amount. become.

This not only increases the power consumption of the video camera and accelerates the consumption of the battery, but also causes the heat generation of the motor itself to adversely affect other systems.

In order to deal with this problem, the method shown in the following third conventional example is considered. This third conventional example will be described with reference to FIGS. 12 and 13.

FIG. 12 shows the structure of the third conventional example. Elements 1 to 8 are the same as those of the first conventional example shown in FIG. 5, and 9 is a resistor. P ₁ shown in the microcomputer 6 is an output port from the microcomputer.

FIG. 13 shows the drive waveforms of this system, up to the time t ₁ as in the first conventional example.
The motor is rotating. Times t ₁ to t ₂ represent waveforms when the motor is stopped. During this period, the output port P ₁ of the microcomputer 6 is changed from the “H” level to the “L” level, and the potentials of the inputs V _C1 and V _C2 of the motor drivers 1 and 2 are lowered via the resistor 9.

As a result, the applied voltage applied to the coils 3 and 4 is lowered as shown in OUT1 to OUT4 in FIG. The voltage value lowered at this time is set to a voltage value capable of maintaining the minimum torque that the rotational position of the motor does not move due to external vibration or the like, that is, the holding torque. Also,
The timing at which the output port P ₁ of the microcomputer 6 changes when the rotation of the motor is stopped is calculated by the microcomputer 6.

Further, as in the second conventional example, in which the voltage applied to the motor itself is controlled by the D / A conversion output of the microcomputer 6, etc., the D / A output is lowered when the motor is stopped. It is controlled in the same manner as the third conventional example. In this case, the timing, voltage value, etc. are set on the program of the microcomputer 6.

[0030]

However, in the second and third conventional examples, the minimum voltage value is obtained while the motor is stopped, but still when the motor is rotating at all. , The same voltage as when rotating at maximum speed is applied.

In the autofocus system of a video camera, the time when the optical system is actually driven at the highest speed depends on the subject to be photographed and the photographing method of the photographer, but is extremely small with respect to the entire photographing time. It is often very short. Also,
Even when the system determines that the focus state of the optical system is in focus, it does not stop the motor completely, but makes a so-called wobbling operation that reciprocates in the vicinity of the focus with an extremely short width. In some cases.

In the case of such a system, the motor hardly stops, and the motor is rotating at a low speed for most of the photographing time. Therefore, the power consumption of the video camera is hardly reduced.

Therefore, in view of the above points, an object of the present invention is to
It is an object of the present invention to provide a motor drive device that reduces power consumption.

[0034]

To achieve the above object, the present invention stops, rotates and reverses a motor by one or a plurality of signals input from the outside, and further applies a voltage to the motor by an external signal. A motor drive device capable of controlling the motor, the means for detecting the rotation cycle of the motor, the counting means reset by the detection result of the detecting means, and the applied voltage of the motor changed by the counting result of the counting means. And a means for controlling the applied voltage of the motor according to the rotation cycle of the motor. Here, the means for controlling the applied voltage of the motor may be a time constant circuit using a resistance and a reactance element.

[0035]

According to the present invention, the motor drive system is provided with means for detecting the rotation cycle of the motor and a counting circuit which is reset by the detected force of the rotation cycle of the motor. By lowering the voltage of the applied voltage control input to a certain predetermined voltage value, the applied voltage can be adjusted to match the rotation speed of the motor even when the motor is rotating at low speed, and power consumption can be kept to the minimum necessary. it can.

[0036]

EXAMPLES Examples of the present invention will be described in detail below.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a diagram showing the configuration of a motor drive system to which the present invention is applied. In FIG. 1, elements 1 to 7 are the same as those of the conventional example shown in FIG. 5 or FIG. 9, 9 is a detector for detecting the rotation cycle of the motor, 10 is a counter for counting at a constant cycle, 11 to 11 Reference numeral 14 is a resistor, and 15 to 18 are switching elements.

FIG. 2 is a diagram showing the input / output relationship and the timing thereof in the embodiment shown in FIG.

The microcomputer 6 shown in FIG. 1 has the same structure as the first conventional example with respect to the driver circuits 1 and 2 and has IN1 to IN shown in FIG.
The rectangular wave signal shown in FIG. The rotation speed of the motor at this time is PE in FIG. 2 if the rising or falling section of each rectangular wave from IN1 to IN4 is one cycle.
It can be detected as shown in RIOD.

FIG. 3 shows an example of an internal circuit of the detector 9 shown in FIG. In FIG. 3, 91 to 94 are monostable multivibrators, and 95 is a 4-input OR circuit. When the outputs IN1 to IN4 from the microcomputer 6 are input to the monostable multivibrators 91 to 94, the outputs of the monostable multivibrators 91 to 94 are I.
A short-width pulse waveform synchronized with the rising of each rectangular wave of N1 to IN4 is output. Each of these outputs is logically ORed by the OR circuit 95 to form a pulse train synchronized with the drive cycle of the motor as shown by OR in FIG.

The timer circuit 10 shown in FIG.
It is composed of a binary counter and counts up by clock input and decodes the count value to generate Q ₀ to Q.
_It is output as ₃ . Q _{0 to} Q ₃ are reset to “HLLL” by the reset input, and the count advances and the count is stopped from the time when the count value becomes 3, that is, Q ₃ becomes H, until there is a reset input. The outputs Q _{0 to} Q ₃ are connected to the control inputs of the switch elements 15 to 18, respectively, and when each input becomes H, each switch element is turned on.

FIG. 4 shows the relationship between the rotation cycle of the motor and the applied voltage required to obtain the rotation torque of that cycle. The time when the counter 10 is reset is shown in FIG.
When the counter 10 starts counting and the count value “1”, that is, the time when Q ₁ becomes “H” is T ₁ , the required applied voltage in the rotation of this cycle is V ₁ .

Similarly, when the count value is "2", the cycle T₂ so
Applied voltage V₂ , "3" is the cycle T ₃ Applied voltage V₃ When
Become.

The cycle of the maximum rotation speed in the motor drive system is represented by T ₀ , and the applied voltage at this time is V _0.
Is. Further, when the motor is stopped, that is, when the cycle is ∞, the applied voltage is represented by V ₄ , which corresponds to the holding voltage.

When the ratio of the output voltages V ₁₂ and V _{34 to} the input voltages V _C1 and V _C2 of the control inputs of the driver circuits 1 and 2 shown in FIG.

[0047]

[Equation 2] V ₁₂ / V _C1 = V ₃₄ / V _C2 = k (2)

[0048]

[Equation 3]

[0049]

[Equation 4]

[0050]

[Equation 5]

[0051]

[Equation 6]

So that the resistors 11/12/13/14
The respective resistance values R ₁₁ , R ₁₂ , R _13, and R ₁₄ are defined.

Counting by the counter 10 progresses and Q ₀ ~
Each time each output of Q ₄ becomes “H”, the switching elements 15 to 18 connected to each are turned on, the resistors 11 to 14 are grounded, and the predetermined voltage corresponding to each state is obtained. Is output.

The area A shown in FIG. 2 shows the drive waveform of each part when the motor is at a medium speed, that is, when the cycle T is T ₂ <T <T ₃ .

By the drive pulses IN1, IN2, IN3, IN4 from the outputs A, A-, B, B- of the microcomputer 6,
The drive cycle is detected by the detector 9 and output as indicated by OR.

The counter 10 starts counting after being reset by this OR, and when the count value is "0", Q
_{When 0} becomes H, the voltage indicated by V _CC · R ₁₁ / (R ₇ + R ₁₁ ) is input to the control inputs V _C1 and V _C2 of the driver circuits 1 and 2, and the driver circuit outputs OUT1 and OUT4 are output.
Outputs the voltage required for the highest speed rotation indicated by V ₀ .

Similarly, when the count value is "1", the voltage V ₁ is output, and when the count value "2" is reached, the voltage V ₂ is lowered. After that, the counter 10 is reset by OR, and the voltage becomes V ₀ again.

This process is repeated, and the voltage applied to the coils 3 and 4 of the motor does not fall below V ₂ in the area A, and the motor is driven at a medium speed.

The area (a) shows the driving waveform of each part when the motor is almost at the maximum speed, that is, when the cycle T is T ₀ <T <T ₁ . At this time, the output of the detector 9 continues to reset the counter 10 with a short width, and the counter 10 is reset while the count value goes from “0” to “1”, so that the count value remains “0”. . Therefore, the voltage applied to the coils 3 and 4 of the motor remains the required applied voltage V ₀ at the time of maximum speed driving, and the motor is driven in a state close to the maximum speed.

The area C shows the drive waveform of each part when the motor is at a low speed, that is, when the cycle T is T ₃ <T. For a long period T, the count value of the counter 10 a while be reached "3" is not reset, the voltage applied to the coils 3, 4 drops to V ₃ of the minimum voltage. At this voltage, the power consumed by the motor is minimal and, in addition, the motor can rotate slowly.

When the rotation cycle of the motor is longer than the cycle indicated by the area C, the period of the minimum voltage V ₃ becomes longer and the power consumed becomes smaller.

Embodiment 2 In the embodiment described above, the means for changing the voltage of the applied voltage control input of the motor driver is composed of the counter, the resistance and the switching element. This means uses the resistance and the reactance element. It can also be configured.

FIG. 14 is a block diagram of an embodiment based on such a configuration. 14, elements 1 to 6 and 9 are the same as those in the first embodiment shown in FIG.
Reference numerals 20, 21 and 22 are resistors, 23 is a capacitor, 24 is a switching element, and 25 and 26 are operational amplifiers constituting a voltage follower.

FIG. 15 is a timing chart showing waveforms at various portions during the operation of the second embodiment shown in FIG.

The drive cycle of the motor is the same as in the first embodiment.
It is detected by the detector 9 and output as indicated by OR in FIG. On the other hand, the power supply voltage V _CC is equal to the resistances 19, 20, 21.
Is divided by two operational amplifiers 25 and 26 which form a voltage follower and have two voltage values V ₀ / k and V ₄
/ K is converted into impedance and output. V shown here
₀ and V ₄ are the required applied voltage V at the maximum speed rotation shown in FIG.
It is the same as the required voltage V ₄ for obtaining ₀ and the holding torque at the time of stop.

Therefore, the resistance value R of the resistors 19, 20, 21 is
₁₉ , R ₂₀ , R ₂₁ are

[0067]

[Equation 7]

[0068]

[Equation 8]

It is defined that

The trigger of the output OR of the detector 9 turns on the switching element 24 to charge the capacitor 23.
At this time, V ₀ / k is given to the control inputs V _C1 and V _C2 of the motor drivers 1 and 2, and as time passes t

[0071]

[Equation 9]

The potential decreases on the curve represented by. Here, C ₂₃ and R ₂₃ represent the capacitance of the capacitor 23 and the resistance value of the resistor 22, respectively. The values of C ₂₃ and R ₂₂ are determined so as to be along or include the curve shown in FIG.

[0073]

As described above, according to the present invention, the motor drive system is provided with the means for detecting the rotation cycle of the motor and the counting circuit reset by the detection output of the rotation cycle of the motor. By lowering the voltage of the motor driver applied voltage control input to a certain predetermined voltage value, the applied voltage is adjusted to match the rotational speed of the motor even when the motor rotates at a low speed, and the minimum power consumption is required. You can keep it to the limit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a motor drive system according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing the operation of FIG.

3 is a circuit diagram showing an internal configuration of a detector 9 shown in FIG.

FIG. 4 is a diagram showing a relationship between a rotation cycle of a motor and an applied voltage required to obtain a rotation torque of the cycle.

FIG. 5 is a diagram showing a conventionally known motor drive circuit (first conventional example).

FIG. 6 is a detailed circuit diagram of driver circuits 1 and 2 shown in FIG.

FIG. 7 is an explanatory diagram showing the operation of FIG. 6;

FIG. 8 is a waveform diagram of general two-phase excitation.

FIG. 9 is a diagram showing another known motor drive circuit (second conventional example).

10 is a waveform chart showing the operation of FIG.

FIG. 11 is a diagram showing the relationship between the rotation speed and the torque of the pulse motor.

FIG. 12 is a diagram showing another known motor drive circuit (third conventional example).

13 is a waveform chart showing the operation of FIG.

FIG. 14 is a block diagram showing a second embodiment of the present invention.

15 is a waveform chart showing the operation of FIG.

[Explanation of symbols]

 1, 2 Driver circuit 3, 4 Pulse motor coil 5 Magnet 6 Microcomputer 9 Rotation cycle detector 10 Counter

Claims (2)

[Claims] 1. A motor drive device capable of stopping / rotating / reverse rotating a motor by one or a plurality of signals input from the outside, and further controlling a voltage applied to the motor by a signal from the outside, the rotation of the motor. A cycle detecting means, a counting means that is reset by the detection result of the detecting means, and a means that changes the voltage applied to the motor according to the counting result of the counting means. A motor drive device characterized by controlling an applied voltage of the motor. 2. The motor drive device according to claim 1, wherein the means for controlling the voltage applied to the motor is a time constant circuit using a resistor and a reactance element.